Currently, in the field of illuminating lamps, electrical products, automobiles and the like where heat resisting property is required, parts of a cured product of a thermosetting resin are used. In addition, injection molding is known as a method of molding a thermosetting resin. In general, however, a cured product of a thermosetting resin is brittle, fragile, and tends to adhere to the metal mold, and therefore, is difficult to release from the mold. In addition, when a thermosetting resin is charged to the cavity of the metal mold, a part of the resin covers the inner wall of the cavity before the resin is sufficiently charged into the cavity, and the resin is further heated and cured, and consequently, bubbles can possibly remain in the molded article in some situation.
When the above-mentioned problems of damaging at the time of releasing and residual bubbles occur, the molded article is difficult to be used as an optical device. In view of this, a method for solving the above-mentioned problems has been proposed (see, for example, PTL 1).
The molded article disclosed in PTL 1 is manufactured by injection molding using a liquid thermosetting resin having a low viscosity. FIGS. 1A and 1B illustrate a configuration of molded article 30 disclosed in PTL 1. FIG. 1A is a plan view, and FIG. 1B is a sectional view taken along line A-A of FIG. 1A. As illustrated in FIG. 1A, molded article 30 is formed in a sheet-like shape. In molded article 30, a plurality of optical device parts 14 are arrayed. Optical device part 14 includes optical function part 11 having an optical function, and outer periphery part 12 disposed outside optical function part 11. Optical function part 11 and outer periphery part 12 are integrally molded. In addition, cutting part 16 for separating optical device parts 14 is provided between optical device parts 14 adjacent to each other.
In the molding of molded article 30, a plurality of optical device parts 14 are integrally molded in one cavity. At this time, the side surfaces (except for the outer surface of optical device part 14 disposed on the outside) of optical device parts 14 make contact with the respective side surfaces of adjacent optical device parts 14, without making contact with the inner wall of the cavity. Accordingly, in comparison with the case where optical device parts 14 are individually molded, the contact area between optical device part 14 and the inner wall of the cavity is small, and the force which is exerted on molded article 30 at the time of releasing is reduced. In addition, depending on the shape and the thickness of outer periphery part 12, the strength of molded article 30 can be increased and concentration of the stress during the molding can be moderated. As a result, deformation and damaging of molded article 30 at the time of releasing can be reduced. Further, the smaller contact area between optical device part 14 and the inner wall of the cavity results in the smaller difference in flow rate between the surface of the resin and the inside of the resin. Thus, residual bubbles in molded article 30 can be reduced. Accordingly, molded article 30 disclosed in PTL 1 can be manufactured without causing damaging at the time of releasing or residual bubbles, and it is possible to efficiently manufacture two or more optical devices by separating optical device parts 14 from molded article 30.